This study is a multicenter prospective randomized controlled clinical trial that will evaluate the use of TC99M-Sestamibi scanning as an aid in ED triage of patients with symptoms suggestive of acute cardiac ischemia, who have normal or non-diagnostic EKG's. The study will determine the impact of sestamibi scanning on accuracy of ED triage decisions: the degree to which those with ACI are discharged. A secondary aim of the study will be to evaluate the impact of sestamibi scanning on hospital costs.